To the original poster... are you talking about aquariums vs photography or just any hobby vs photography in general? Your post didnt mention anything.
If you are, it definitely depends on your situation in life. I got into reefkeeping, then FOWLR, then photography, then I sold my FOWLR due to my new daughter and not having time for the tank, then I got back into FOWLR in the last 6 months once my daughter turned 6 months old and I had some time again to just goof around.
It's very hard to make a call as to which one I would do first, but with having a family and a little daughter I want to make memories of, I'd definitely go with photography first, however that's just me. If you dont have a lot of stuff you want to take pictures of, then go reef.
You could also rent from one of the online companies for a week or two, get a nice body and lens and just goof around and see if it's something you like. If not, you're just out $100-$200 and can decide to go reef aquarium for sure.